Scavenging the cylinders of doublebore cylinder combustion engines



Dec. 26, 1939. om- 2,184,603

SCAVENGING THE CYLINDERS 0F DOUBLE-BORE CYLINDER COMBUSTION ENGINES Filed Aug. 16, 1937 2 Sheets-Sheet 1 Dec. 26, 1939. A. PORTMANN 2,184,603

SCAVENGING THE CYLINDERS 0F DOUBLE-BORE CYLINDER COMBUSTION ENGINES ZSheets-Sheat 2 Filed Aug. 16, 1937 BAA v I fine/2501':

I 7AM" @MMIML/ ATM Patented Dec. 26, 1939 UNITED STATES SCAVENGING THE CYLINDERS OF DOUBLE- BOBE CYLINDER COMBUSTION ENGINES August Portmann, Winterthur, Switnerland, assignor to the firm Schwelzerische Lokomotivund Maschinenfabrik, Winterthur, Switzerland Application August 16, 1937, Serial No. 159,412 In Germany August 17, 1936 scum.

This invention relates to the scavenging of the cylinders of double-bore-cylinder internal combustion engines, the two bores of each cylinder of which being interconnected at the ends thereof adjoining the cylinder head by a communication channel and the scavenging air entering one of the cylinder bores at the lower end of the piston swept surface thereof and discharging at the lower end of the piston swept bore surface of the other cylinder. In double-bore-cylinders of this kind, the communication channel must be kept down to small dimensions with a view of obtaining an adequately high compression pressure, in consequence of which, the narrow cross section provided for this channel, in conjunction with the requirement of diverting the flow of scavenging air therethrougli, causes local accumulations of inert gases particularly in the exhaust cylinder, during the scavenging operation.

According to this invention these diiliculties are met by giving the cross section of the intermediary passage a substantially oval shape.

In the accompanying drawings several constructional forms of double-bore-cylinders are illustratively exemplified for explaining the apparatus according to the invention as this is applied to these cylinders. In these drawings:

Fig. 1 is a vertical sectional view on the line I-I of Fig. 3 of a double-bore-cylinder of a first constructional form in which the scavenging air is imparted a twist at its entry into the admission cylinder bore;

Fig. 2 is a sectional view on the line 1III in Fig. 1;

Fig. 3 is a sectional view on the line III-III in Fig. 1;

Fig. 4 is a sectional view of a detail on the line IVIV in Fig. 3;

Fig. 5 is a sectional view similar to Fig. 1 of a double-bore-cylinder of'a second constructional form in which the scavenging air is imparted a twist in the exhaust cylinder bore;

Fig. 6 is a sectional view on the line VI-VI in Fig. 5;

Fig. '7 is a sectional view of a modified detail of Fig. 6;

Fig. 8 is a sectional view, similar to Fig. 5, of a double-bore-cylinder of a third constructional form in which the communication channel is provided with an insert;

Fig. 9 is a sectional view on the line IX-IX .in Fig. 8, as seen in the direction of the arrows shown;

Fig. 10 is a sectional view on the line x-x in F 8;

Fig. 11 is a schematic sectional view illustrating the path of the helical flow of scavenging air as diverted by the communication channel.

Fig. 12 shows the assembled engine. 1

In all figures of the drawings, the pistons 01 a: cooperate with a pair of cylinders b connected by a common combustion chamber, the cylinders being cooled by means of a cooling water Jacket h. The manner in which the pistons 61,02, that is, the piston rods in, b: are operatively connected with the crankshaft, is not shown as this is a matter known per se. The two cylinder bores intercommunicate through the communication or intermediary channel or passage i. The scavenging air enters the admission cylinder bore 01 through slots 01, which are opened by the admission piston 111 when the latter is in the vicinity of the lower dead center thereof, and discharges from the exhaust cylinder bore 02 through slots 0:

entering the entrance in the direction of the arrow to the left in Fig. 1 is given a twisted or helical direction by the provision of the ribs 9 between the individual slots 01, said ribs being constructed as guide vanes inclined to the radial direction as indicated by the arrow R. In order to obtain a uniform distribution of scavenging air over the entire cylinder bore circumference, special guide vanes q of greater length are provided which have the effect that the entrance slots situated in the space m are also supplied with an adequate amount of scavenging air entering in the required direction. Alternatively, several vanes q may be distributed over the circumferenge of the entrance. The disposition of the vanes p depends upon the twist or whirling movement to be imparted to the scavenging air. When it is desired-,to maintain the whirling movement only in the entrance cylinder bore, it suflices to impart to the flow of scavenging air less twist than if the whirling movement is to be maintained in the exhaust cylinder bore also.

When it is desired to obtain a whirling movement in the exhaust cylinder bore also, this can be effected in the manner mentioned above by producing in the admission cylinder bore a whirling movement of such high intensity that this movement is maintained by diversion in the communication channel 1, as shown in Fig. 11.

In this case, the intensity of whirling movement is, advantageously, so chosen that in the exhaust cylinder bore also during the scavenging period at least one turn of inherent rotational movement is carried out. The special form of communication channel asshown in Figs. 1 and 2 is particularly well suited for maintaining a continuous helical flow, which form results in a very effective scavenging operation with any kind of scavenging irrespective of whether an inherent rotational movement is set up in the helical flow or not.

Alternatively, the formation of a whirl in the exhaust cylinder bore can be eflected, as shown in Fig. 6, by disposing the axis of the communiis evident-from Fig. 3, the scavenging air.

cation channel i so that it is not in the joining line of the two cylinder bore centres 21, an as is evident, for example, from Fig. 9, but so as to lead into the exhaust cylinder bore in a somewhat tangential direction. By this means a whirl is obtained in the exhaust cylinder bore even when in the admission cylinder no whirl was produced. To the same end, the communication channel may be constructed as shown in Fig. '7, the whirls setting up in the two cylinder bores then having the same direction of rotational movement inherent thereto in all cases where at the same time in the admission cylinder bore a whirl is produced. By means of the arrangement shown in Fig. 6'the whirls in the admission as well as in the exhaust cylinder bore have inherent thereto rotational movements of different directions.

The transfer of a whirl set up in the admission cylinder bore into the exhaust cylinder bore is facilitated by giving the communication channel 1 a substantially oval shape, as shown in Figs. 2 and 10, due to the fact that this cross sectional shape highly contributes to maintaining the whirling movement, as tests have shown. Advantageously, the intensity of the whirling movement is so chosen that this movement is maintained even during the ignition and combustion periods, so that in injecting the fuel in the tangential direction, as indicated by the arrow w in Fig. 2, the fuel is excellently admixed in the direction of the corresponding arrow and burnt.

By giving the admission piston a1 a shape as shown in Figs. 1 and 8 the guidance of the whirl is improved in that the chamfering a: forms together with the adjacent cylinder wall a circumferential groove. The chamfering along the line a: has the further advantage that the combustion space is given a somewhat concave shape while at the same time the piston end face is convexed by the guide surfaces thus formed, so

that the entry of the scavenging air into the channel i is faciliated in that, in this way, an eased ofi corner is formed at d1, which prevents the accumulation of inert non-scavenged gases. In this case, the exhaust piston head can be made flat-ended as shown in the Figs. 1 and 8, without any detrimental efiect, as regards the combustion space, so that the heat transmission to the exhaust piston which is subjected to higher temperatures is facilitated.

With a view of obtaining a satisfactory scavenging of the entire space above the exhaust piston a: when the helical flow leaves the exhaustcylinder bore ca in the direction of the arrow to the right in Fig. l, the exhaust slots remote from the admission cylinder bore are shortened as, at r, in Fig. 4. This shortening may be provided, for example, for three slots 0:, as indicated in Fig. 3. By this means the discharging scavenging air is compelled not merely to follow the shortest path away from the connecting channel 2' to the exhaust space, but rather to discharge with a uniform'distribution over the whole circumference of the exhaust cylinder and thus to sweep all portions of the interior of the exhaust cylinder bore for scavenging the same.

The cylinder may be cooled by means of air instead of water in which case the cooling water jacket h is dispensed with and instead the cylinder b is provided with cooling ribs t (Fig. 12).

Various changes and modifications may be made in my invention without departing from its principle, by simply applying customary practice and established knowledge of the art to the present disclosure.

What I claim is:

1. In a combustion chamber connecting a pair of internal combustion engine cylinders successively scavenged by a vortex of air, means forming a combustion space extending substantially in a line joining the centers of the bores of said two cylinders at the upper end of the piston swept surfaces of said bores and provided with a cross section lying in a plane extending transversely of said joining line centrally between said bore centers in parallelism with said bores, and having an oblong-shape with rounded out corners, the longitudinal axis of the oblong being directed substantially perpendicularly to said bores, for reducing the height of said combustion space and guiding the rotating masses of said vortex circumferentially of said cross-section.

2. In an internal combustion engine having a pair of cylinders connected by a common combustion chamber and successively scavenged by a vortex of air, means forming in the preceding cylinder bore at the lower end of the piston swept surface thereof an air entrance having radially directed distributing surfaces of various sizes for uniformly distributing said vortex over the circumference of said bore, and means forming a combustion space extending substantially in a line joining the centers of the bores of said two cylinders at the upper end of the piston swept surfaces of said bores and provided with a crosssection lying in a plane extending transversely of said joining line centrally between said bore centers in parallelism with said bores, and having an oblong shape with rounded out corners, the longitudinal axis of the oblong being directed substantially perpendicularly to said bores, for reducing the height of said combustion space and guiding the rotating masses of said vortex circumferentially of said cross-section.

3. In an internal combustion engine having a pair of cylinders connected by a common combustion chamber and successively scavenged by a vortex of air, means forming a combustion space extending substantially in a line joining the centers of the bores of said two cylinders at the upper end of the piston swept surfaces of said bores and provided with a cross-section lying in a plane extending transversely of said joining line centrally between said bore centers in parallelism with said bores, and having an oblong shape with rounded corners, the longitudinal axis of the oblong being directed substantially perpendicularly to said bores, for reducing the height of said combustion space and guiding the rotating masses of said vortex circumferentially of said cross-section into the succeeding cylinder bore, and means forming in said succeeding cylinder bore at the lower end of the piston swept surface thereof an exhaust opening, means forming exhaust passages, gas guide surfaces situated in said opening in advance of the outlet thereof and arranged circumferentially of said succeeding cylinder bore, a plurality of said exhaust passages being located in said outlet remote from the preceding cylinder bore and being arranged substantially flush at the top with other exhaust passages, the other exhaust passages being of greater vertical extent than said plurality of exhaust passages for uniformly distributing the discharge of gas around the circumference of said succeeding cylinder bore.

' AUGUST PORTMANN. 

